


The Chase

by cliteastwood



Category: The Departed (2006)
Genre: Alternate Universe - Canon Divergence, Canon-Typical Violence, Dubious Consent, Homophobic Language, M/M, Restraints
Language: English
Status: Completed
Published: 2019-11-10
Updated: 2019-11-10
Packaged: 2021-01-26 14:37:06
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,852
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21375727
Author URL: https://archiveofourown.org/users/cliteastwood/pseuds/cliteastwood
Summary: What if Costigan didn't hang up on Sullivan when he called from Queenan's cell phone? What if he agreed to meet up?
Relationships: Billy Costigan/Colin Sullivan
Kudos: 17





	The Chase

**Author's Note:**

> Goes AU/off-script from the end of the italicized portion of the phone call at the very beginning. Based off my personal headcanon that Sullivan's gay and closeted. So very self-indulgent but I hope others enjoy :)

_"Yeah?"_

_"You called this number on a dead guy's phone. Who are you?"_

_"So it is you. Thank god you're alright. We were very worried."_

_"Who are you?"_

_"This is Sergeant Sullivan. I'm taking over Queenan's unit."_

_"Let me talk to Dignam to confirm it."_

_"Staff Sergeant Dignam is on a leave of absence. He's very upset. We're all very upset. I mean, I think the best thing would be for you to come in. We need you to come in. Can you come in? Or meet me—"_

Billy doesn't hang up but he does scoff audibly. Can't help it; he's not stupid and this reeks of a setup.

"Okay, you're scared to meet me with the rat still on the job. I get that, but—"

"I'm not fucking scared. Meet me on the roof where Queenan died. Tomorrow. Midnight. Alone. If this gets back to Costello, you're a dead man."

He slams the phone shut this time, heart pounding. He may have said—and _meant_—he isn't scared, but he is nervous as all hell. The one number he has for Dignam is his office phone and he clearly isn't gonna be answering that anytime soon. Queenan's dead and hadn't mentioned any other cops around the department he could trust. So, the way Billy sees it, he has two options: he can trust this Sullivan fuck to be on the straight and narrow and lay bare all his intel, or he can trust his gut that this is a trap and ambush the sarge before he has a chance to snuff him out. As he eats another two pills, he knows what he's gotta do.

\-----------------------

Costigan spends the entirety of the day trying not to shit his pants, sussing out whether or not Costello thinks anything's up with his police connect. They wind up at one of Frank's bars after dinner, a rare slow night with no deals to be made. Costello's still in good spirits from Captain Queenan's death but he's not paying Billy any special attention that would make him think he knows about the meeting. French has just wrapped up a lengthy, gross, and probably fictitious story about a threesome he had some years back. When Billy glances at his watch, he notices it's almost 11 and he better hustle if he wants to beat Sullivan to the warehouse. Begging off another round, he goes for sheepish to avoid many follow-up questions when he mumbles something about having a 'date type thing' and hauls ass to his car.

He chain smokes the entire drive and goes back over the plan. He's got his gun, that's a given, but he's also got a set of handcuffs in his back pocket. He has no clue what to expect but he knows he'll want to take control of the situation pretty quickly; have a gun on the prick as soon as he's got an eye on him and make the cuffs follow a second later. How many times did he drill exactly this situation in the academy? It's wild realizing that tonight, with literally _no one_ watching his back, is going to be one of the first opportunities Billy has to put any of his police procedures to use.

Trying to harness his adrenaline, Billy shuts off his car and begins walking the meandering path to the back side of the building. It's dark enough and sleazy enough a neighborhood for him to skulk through unnoticed and the trek helps clear his head. Costigan's been in a thousand situations these past few months that require absolute focus, where the slightest mistake can cost him his life, and yet this is the only one where he's been even remotely in control. He's not confident, not by a long shot, but it's nice to feel prepared. As his eyes stay downcast, scanning the sidewalk outside the abandoned building, he's glad to see they've at least done a good job cleaning up the crime scene.

The entire walk up the stairs to the meet spot is eerie. Billy's got his flashlight to keep him from busting his ass, but visions of the last time he was here threaten to trip him up. He's going up rather than down the fire escape but his muscle memory kicks in just the same. He can't slow down if he tries; he's a man on a fucking mission tonight and if he stops running, he's dead.

\-----------------------

It's a good half hour before Billy hears it, the door to one of the inside stairwells slamming shut. He closes his eyes and hones in on the noise, carefully listening for anything unexpected. Billy's well aware that he might be met by more than just this Sergeant Sullivan, an honest-to-god coin toss whether it'll be an army of cops or an army of gangsters accompanying him. But for some strange reason, Costigan can just sense that Sullivan's kept his word. Well, some strange reason plus the sound of rapidly approaching footsteps, decidedly fewer than a cavalry's worth.

Billy's at the ready when the door to the roof flies open. He can't see shit besides the door itself initially, but he's behind it nonetheless. The guy steps out just enough for Billy to confirm he's alone and instinct takes over. Before he knows it, he's got the muzzle of his gun flush against the sergeant's skull.

"On your fucking knees now. _Now._ Hands behind your head."

Costigan doesn't recognize his own voice—it's Uncle Jackie if it's anyone—but it's effective. The sergeant goes down in one fluid motion, fingers linking together against the back of his head like maybe this isn't his first time being shaken down. Billy prods Sullivan's lower legs with his right foot while he uses his free hand to pat down his upper body. Finding and confiscating only the one gun at his waist plus a pocketknife, Costigan considers forgoing the handcuffs. Unlikely that any mobbed up asshole worth his salt would be caught unawares and let himself get disarmed at a planned meeting. An overworked cop desperately trying to connect with his case's last hope? Maybe. But trust and faith are emotions of desperation, of having no other option. The benefit of the doubt only benefits whoever's fucking lying and it may as well be Billy this time—lying through his actions that he's cut out for this shit.

So he pries Sullivan's hands down to his lower back, one at a time, and secures them with the cuffs. It's only when he has a chance to take in the whole picture that he realizes what's sickeningly familiar about it. That ball cap. That hoodie. That fucking blade he just pulled off the guy. It's him; it's the rat. Costigan committed the back of this scumfuck's head to memory the night he almost caught him. The night the prick stabbed an innocent man to death because he thought it was Billy. He knows it in his bones like he knows his entire destiny hangs on the precipice of this moment. Seems Sullivan didn't get the memo and still thinks he's walking out of here unscathed.

"Feel better? Now put the gun down and let's talk."

Billy figures showing himself at this stage is pretty low risk and there's only so much of that Southie accent he can fucking take, especially when it's barking orders at him from the vicinity of his cock. He holsters his gun and heaves Sullivan upright by his armpits, pinning him to the wall next to the door he just came through. They're face to face for the first time and it's jarring. It's not what he expected Costello's rat to look like, that's for damn sure. This guy's his fucking age and a _sergeant_; he's not even ugly. There's no fucking reason for him to be selling out like this when he's got brains, looks, and ambition.

It pisses him off irrationally and he responds by yanking the American flag cap off the dirty cop's head by the bill and following up with a punch straight to his stupid nose. The one-two combo has him doubling over, wheezing and stumbling and dripping a little blood. Costigan shoulder-checks him against the wall once he gets his bearings back, much to Sullivan's confusion.

"Fuck you, you fucking prick! What the hell was that for?! I'm trying to save your ass here! I'm your fucking handler now."

Disgusted that this guy still thinks he's gonna skate, livid that this guy isn't groveling like the fucking worm he is, Billy throws the full weight of his body against Sergeant Sullivan. If he gets a heady rush of power from the fear he sees a flash of in the other man's eyes, that's nobody's business but his. He doesn't back off, not an inch, as he sizes up his ensnared prey.

"I can't believe you still think you've got everyone snowed, you rat fuck. I know who you are—I know _what_ you are."

"You don't know shit."

The assertion is weak, feeble, and at first Billy thinks it's because Sullivan finally accepts that he's sunk. Then he feels it. The guy's only an inch or two shorter so it's right against his fucking thigh, hard and hot and obvious. For all his mental preparation, this is one turn of events he never saw coming. What kind of fucked up faggot gets his rocks off being handcuffed and beaten up? What kind of repressed, self-denying cumstain gets hard from even the roughest of touches from another man? Those types of questions keep Billy from asking a more important one: _What kind of sick fuck takes advantage of a situation like this?_

"Oh yeah? 'Cause I think I'm learning more of your secrets by the second. Or does everybody already know you're a queer, huh?"

"Shut the fuck up, I'm no fucking queer."

Billy exhales with a disbelieving little laugh and brings his leg up and in, rubbing deliberately against Sullivan's dick. Sullivan doesn't grind back against him, not exactly, but the expected disgusted recoil never comes. Billy shakes his head, feigns disappointment.

"See, you say that, but your cock's telling me a different story. I don't like being lied to, so why don't you just fucking admit it?"

"What do you want? Me to suck your dick? Let's get it the fuck over with then."

The guy's dead serious and it gives Billy pause. He wonders how this situation got so far away from him. Jesus Christ, he's not gonna sexually assault anybody. He steps back, like that might help him regain some clarity or control, but Sullivan just takes that as permission to drop to his knees once again. Billy blinks and the sergeant's nose-to-dick with him. His normally finely tuned fight-or-flight response goes out the window and he's frozen. Can't even look away as he's outright nuzzled through his jeans. Somewhere between Sullivan starting to lick and nip and Costigan beginning to get hard himself, he decides, _fuck it._ The rat's pretty damn eager and pleasure's a hot commodity in this line of work.

Billy steps back once again, throwing Sullivan off balance. To right himself, the guy has to spread his thighs and lean back on his heels, unintentionally displaying his slick, swollen mouth and his still-hard cock. The sergeant locks eyes with Billy in real, unadulterated panic, no doubt believing his advances are being rejected and expecting to be killed. Costigan smirks and drops his attention to where he's busy undoing his own pants, knowing Sullivan's eyes will follow. Careful not to dislodge the guns at his waist, he pulls his jeans and underwear down just enough to get his cock out. Billy strokes it a couple of times, stares hard at Sullivan until the rat finally notices and pulls his gaze back upward.

"You want it, you can come get it. I ain't forcing you to do shit."

It's a dirty tactic, at least where Sullivan's pride is concerned, but Billy seriously isn't about to make a guy blow him under threat of death. Their eyes remain locked; it reminds Billy of a childhood staring contest. He's just starting to feel ridiculous about still having his dick out when Sergeant Sullivan caves. He doesn't blink but he huffs out a put-upon sigh and shuffles forward the scant inches necessary to put him back in contact with Billy's cock.

Without the use of his hands, he's pretty limited in what he can do, but Costigan kindly assists him by cradling the back of his head and resting the wet tip of his dick on the sergeant's fat bottom lip. It seems that's all the encouragement Sullivan requires because he opens up right away, guarding his teeth and sucking without needing to be told. He's not gonna be winning any deep throat competitions anytime soon, but Billy's impressed with the rat's enthusiasm. Once he's got a nice little rhythm going, Billy lets go of his cock and runs his fingers through Sullivan's short hair, using both hands to help guide him slowly back and forth.

It certainly doesn't seem like the sergeant is taking this to be much of a punishment. The subtle tells are there—the little grunts; the aborted half-thrusts of his hips into nothing but air; the sheer talent of that fucking tongue, going above and beyond what's necessary to get Billy off. If anything, Billy suspects, the poor guy's even harder now than when he was pinned to the wall. Testing his theory, Costigan runs his left foot up Sullivan's right thigh, firm enough to make its presence and trajectory known but light enough not to hurt. And the little rat responds like a dream, pushing his dick into Billy's boot with a garbled moan. The swaying of his hips from his kneeling position forces his head all the way down onto Billy's cock and he's not gagging this time. Billy shoves the side of his fist in his own mouth but he cries out around it anyway.

Costigan's never gotten head like this, from someone who sucked dick like their life depended on it. And he's already made it abundantly clear that isn't the case, so the rat bastard must just love it. He's sloppier than any woman Billy's ever been with, drooling and slurping all over the place and not doing a damn thing to keep the obscene, wet noises down. It'd be easy for Billy to close his eyes, pretend he's fucking a girl but he's gotta admit he finds the real view plenty appealing in its own right. Sullivan's a handsome guy and desperately horny is a nice look on him. The power trip is icing on the cake.

"You're just a natural born cocksucker, huh? This how you got promoted so fast, pretty boy?"

Billy's never been much of a talker but there's just something about this asshole that sets him off. He can't stop himself, a running theme of this entire goddamn mission.

"Gonna shoot all over that pretty face of yours. Mark you up like the slut you are."

Costigan increases the pressure from his boot, grinds it in circles over Sullivan's confined cock and balls. Billy's all but fucking his face now.

"Then I'm gonna call your buddies on the task force, tell 'em where they can—_aw fuck_—find you handcuffed, all covered in my cum, and—"

Billy abruptly breaks off mid-sentence with a growl as his orgasm hits him like a freight train. He almost fails to make good on his threat—Sullivan's sucking the cum straight out of him and swallowing as he goes—but he pulls out quick enough to streak the sergeant's mouth and left cheek, temple to chin, pearly white. Billy uses his fingers to smear the cum over Sullivan's lips and starts working his boot over his cock in earnest. 

Like he can't help himself, Sullivan sucks Costigan's thumb into his mouth. Good thing, too, because the fucking rat is moaning and groaning and cumming in his jeans and Billy's finger is the only thing keeping him from waking up the neighborhood. Billy gives him a few seconds to come down—common courtesy—and then extracts his thumb from the sarge's panting mouth, pats him on the clean cheek with his filthy hand, and zips himself back up. He turns to get the hell out of Dodge, but spares one more glance for the thoroughly humbled and fucked out Sergeant Sullivan.

"So, hey, when I call the cops, you think I oughta tell them you jizzed in your pants or just let them find out when they book you?"

The rat's sputtering as the door slams shut behind Billy. Just as well, he hates long goodbyes. Costigan makes his way downstairs—inside this time, fuck that fire escape—and works a cigarette and lighter from the pack in his pocket. He contemplates his next move—it's a fairly delicate situation, after all—and laughs like a madman when it hits him. 

There can't be _that_ many Sean Dignams in the white pages, can there?


End file.
